Is preschool necessary?

I’m a Sahm and my daughter is currently three. It seems like everyone sends their kids to preschool now, versus when I was a kid it wasn’t as popular. I never went, just went straight to kindergarten. We really don’t find it necessary to pay to send her to preschool when the whole point of my staying home is to not pay for daycare 🤷‍♀️ But I worry she will be behind when she starts kindergarten if the other kids are already used to a school routine.